Male-pattern baldness Hair's something to think about: Bald men may be at higher risk of coronary heart disease.

However those receding from the front can breathe easier as the study published today in the online journal BMJ Open shows the increased risk is only if the hair is lost at the crown.

Researchers from the University of Tokyo's Department of Diabetes and Metabolic Diseases analysed six studies on male pattern baldness and coronary heart disease conducted between 1993 and 2008 with nearly 40,000 participants in the United States and Europe.

They show men who have lost most of their hair were more than a third more likely to develop coronary artery disease than those with hair.

The severity of baldness influenced the degree of risk, but again, only if the balding was at the crown, or vertex.

"These findings suggest that vertex baldness is more closely associated with systemic atherosclerosis (coronary heart disease) than with frontal baldness," the authors write in the paper.

"Thus, cardiovascular risk factors should be reviewed carefully in men with vertex baldness, especially younger men, and they probably should be encouraged to improve their cardiovascular risk profile."

The researchers concede further studies are needed to confirm the findings.

The study says about 30 to 40 per cent of adult men suffer from male-pattern baldness - and up to 80 per cent by the age of 80.

The reasons for the association are unclear, but the authors point to previous links drawn between baldness and insulin resistance, diabetes, chronic inflammation or sensitivity to testosterone; all of which may lead to cardiovascular disease.

All relative

Professor of Statistics at University College London Patrick Wolfe says it is important to understand the study reports an increase in "relative risk" after other factors such as smoking have been taken into account.

"So, if we consider the case of two male, non-smoking marathon runners in top physical condition, one of whom is bald and the other not, then their absolute risks for heart disease are likely to be quite small - despite the fact that their relative risks may be different - both because of baldness and because of other factors, including family history," he says.

Wolfe says the link responsible for this relative risk increase is not well understood.

"We look forward to a day when understanding more about the various mechanisms underlying heart disease will tell us more about those underlying male pattern baldness, and vice-versa," he says.

"In the meantime it's a case of focusing on the things that we can control - our diet, exercise regimens, and other risk factors - to lower our overall risk for heart disease."